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131 Cards in this Set
- Front
- Back
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visual signals: lion's mane
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PERMANENT BADGE
– male shows off by displaying mane -when aggressive, hair stands on end, looks bigger -says I’m a male, I’m aggressive, I’m tough -some animals can derive information from another animal and use that information |
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visual signals: blackburnian warbler
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TEMPORARY BADGE
looks much more vibrant in the spring and mating season -says “I’m a male and I’m available for breeding!” |
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visual signals: magnificent frigate bird
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-When the male doesn’t have offspring or a mate, walks around with throat pouch extended
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visual signals: shark agnostic display
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Can include posture displays
This shark has territory on reef -If an intruder swims into the territory, shark will start such display -nose tipped up so intruder will see teeth -back arch, tail down, flippers down – makes him look bigger than he is -thrashes tail side to side – makes it look bigger horizontally -acts this way until intruder backs off, would escalate behavior only if intruder doesn’t back off |
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graded signals: Stellar's Jar
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Can control position of feather on its head
-when it is comfortable/calm, tuft lays flat -when it is more on edge, tuft becomes higher -different positions communicate different things 0 degree angle – at rest 60 degree angle – courtship – good excited 90 degrees – angry bird, probably involved in an altercation or potential predator |
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composite signal: zebras
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Opposite of grated signal – ALL OR NONE signal – it’s there or it’s not there
Zebras combine both -ears forward = friendly, ears back = aggressive (all or none) -how aggressive or friendly they are depends on what mouth is doing (grated) -ears forward, mouth open – very happy, excited -ears back, mouth open – aggressive, angry, likely to attack |
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metacommunication
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one signal modifies the following signals/communication
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metacommunication in dogs
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If dog does “play bow,” any other action that follows is taken as playful
-actions that could have otherwise been taken as aggressive |
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sound signals (examples)
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Birdsong
Dolphin whistles Cricket chirping Infrasound: elephants, giraffes, maybe hippos (too low for human ear to detect) |
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chemical signal: Bombyx mori
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-purpose of male’s large antenna are to detect female pheromones
-female raises abdomen and releases plume of pheremones -males fly upwind, can detect when they have left the plume so they can correct path and eventually reach female |
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communication function: fiddler crab
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SPECIES RECOGNITION
-not visual creatures, need communication cues to recognize different species -fiddler crab claw – method of movement a sign to the female of species ID |
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communication function: Mate attraction & territoriality
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layback experiments with bird songs
-birds more attracted to songs of their own species Territory: Have three adjacent territories, if male is removed from middle territory, males from either side will momentarily investigate If tape is played in empty territory, males will not investigate for days |
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communication function: courtship
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Function of courtship – get both animals on same page
Blue footed booby: -gets timing of physiological events correct -brighter blue feet more attractive to females – indicate healthier birds -sky pointing – gets birds in sync |
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communication function: agonistic
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shark:
This shark has territory on reef -If an intruder swims into the territory, shark will start such display -nose tipped up so intruder will see teeth -back arch, tail down, flippers down – makes him look bigger than he is -thrashes tail side to side – makes it look bigger horizontally -acts this way until intruder backs off, would escalate behavior only if intruder doesn’t back off |
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agression and submission: elephants
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-measure of size and strength
-trunks = main sensory organ of the elephant -if elephants fight, they will kill each other – especially an angry elephant – VERY AGGRESSIVE WHEN ANGRY -good idea not to get to that point -keep things from escalating |
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communication function: recruitment
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honey bees:
-recruiting other bees to patch of flowers to help gather nectar -one bee gathers nectar, brings it back to the hive, and alerts other bees -Waggle dance- von Frisch -Round dance – lands on honeycomb and makes buzzing noise – dance in a circle – 3m -Waggle dance done when patch is farther away -has extra step in it -starts by waggling in a line, two loops on either side -can communicate distance AND direction -distance – correlated to the number of waggles and to length of time that the waggle run takes -length of dance is always the same – just wigglier or less wiggly -direction – conventions -straight up means toward the sun -tilted opposite correct direction |
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natural selection in signals - honeybee waggle dance
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Bee dances have dialects depending on region. A waggle indicates a greater distance in areas where flower patches are rarer so flights usually longer.
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natural selection in signals based on preexisting behaviors: apes
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Gorilla – larger, can thunder through the forest floor and make noise with hands on chest
Gibbon – more expressive voice/hooting |
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natural selection in signals based on effect of task to be accomplished
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Lepotothorax – small, dead prey
Ex: dead beetle First worker ant – drop of recruitment pheromone Second ant – reaches out with antennae and maintains contact with first ant – tandem walk back -pheremone keeps reinforcing the following behavior FIRE ANTS – very different Largish, mobilish prey -need more recruits for larger prey -volatile chemical trail, when ants smell the trail they follow it back up towards the prey – can get attention of many ants simply by accident -Problem – prey can move -ants come to end of the trail and then start searching -can then start biting, return to the hive setting new trail ALSO, LEAF CUTTER ANTS: -need large continuous supply of leaves -trees aren’t going anywhere -non volatile chemical trail left – doesn’t evaporate like that of the fire ants -this is OKAY because the tree is STATIONARY |
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how natural selection shapes signals: great tit
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-very small bird
-When they see a predatory bird, exhibit mobbing behavior -alarm call – seet call - made when you want everyone to hide -higher pitch, hard for hawks to hear but audible to the great tits -evolution has driven this call into a range that cannot be heard |
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how natural selection shapes the signal based on environment
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In general, sound signals face two kinds of problems
Degradation – sound is blocks by physical structure – sounds waves get distorted Attenuation – weakening with distance In woods, big problem is degradation -in the woodland, birds’ main frequency is around 2 kHz, because that has the least degradation -in the grasslands, main frequency is higher (typically 4 kHz or so) Another problem: higher frequencies attenuate more quickly – Why would they do this when degradation is not an issue? -Male birds perch on higher twigs -”Sitting ducks” – easily spotted by predators -BALANCING EFFECT – bird want song to reach females, but not catch the attention of hawks potentially flying overhead In open areas, there are more trills and repeats than in forested areas -probably due to source of degradation –WIND – in open areas -not a consistent obstacle -trills and repeats make it okay if one part of the song was obscured by gust of wind -songs in woodland more varied, probably because birds are more concentrated -less wory about predators – singing from hiding places |
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honesty: mating toads
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-females prefer larger males
-when males are sitting around making calls, females are attracted to deeper sounds Experiment to see if this also had an effect on other males: -Males croak while riding on the back of a female to advertise how big they are to other potential attacking males -Places rival male in arena with couple -Observed if he attacked, and for how long -Attacked much more often and for much longer when there was a higher pitched croak -Size of the original toad also mattered |
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honesty: barking geckos
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Barking gecko – sounds like a dog bark
-makes deeper bark when bigger |
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honesty: Australian antlered flies
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-the wider the antlers, the bigger the fly
-assess eachother’s antlers, smaller one will back away |
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honesty: dewlap displays and push ups in (WHAT ANIMAL?)
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Duration of threat displays and # of push-ups reflect condition of the male so are an honest signal of how well the male can fight
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honesty: vervet monkeys
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-Why don’t these monkeys make alarm calls to scare other troops away and get all the food?
-Monkeys recognize each other by their calls -Played alarm call when nothing to be scared of -After a few repetitions, the troops start ignoring that alarm call, and that monkey in general -Very specific to the one monkey and his call |
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deceit: pied flycatcher
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-typical kind of songbird – males set up territories then try to attract females to their territories
-females arrive in waves in the spring -if male has a good territory it will be occupied fairly quickly -males sing to attract females -when a female moves in there is no longer a reason to sing, male stops wasting his energy (except for a little to keep other males out of his territory) -if another female shows up on territory, male will sing excessively to intercept her, make her think he’s unmated -can sometimes convince second female to stay on territory by pretending he is unmated if it shows up on his territory -detrimental to second female because he probs won’t get much help raising her offspring |
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deceit: somatopod
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Meral spread – threat display when territory is threatened
-have spring loading on front appendages – use these to knock out prey -when male threatens territory, bad to approach because this spring loading is very dangerous -right after molting, somatopod shells are very soft, but will still do display -very rarely will other somatopod approach – the risk is too great |
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deceit: fiddler crabs
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Original claw in fiddler crabs (Uca mjoebergi) accurately reflects strength of crab, but can grow a weak, light-weight replacement claw
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problem of illegitimate receivers: Female Photuris & male Photinus
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Signals evolved for one purpose and directed towards specific recievers
Other can intercept message and use it, sometimes against you Fireflies -flashing patterns unique to each species -mating system – females fly around flashing (indicating that they are sexually receptive), males fly around looking for flashing females -female photuris (are much bigger), if they are hungry, will flash like female photinus to attract photinus males -female photuris then attracts male in, then eats him |
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Problem of illegitimate receivers: tungara frog & fringe-lipped bat
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-fringe lipped bat – eats frogs (among other things)
-to attract a mate, tungura frog has to make noise – unfortunately this also attracts bats -frog makes whine-chuck call -female ear is particularly sensitive to chucks, calls with more chucks are more attractive -whine necessary for species recognition; chuck role is attractiveness (more and louder) -bats hear chuck call the best -frog has to balance need to attract females with need to survive hunting bats Low density pond: -only make the whine part of the call -identifies species, at low density there is not much competition between males -chances of attracting bat from chuck calls would be higher, less protection from dilution effect High density pond: -more competition among males, chuck call is more necessary -dilution effect makes it less of a risk |
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Evolution of Signals: Ritualization in birds (ex roosters)
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How did these signals (complicated messages like waggle dance) evolve in the first place?
-a lot of them seem to evolve from pre-existing behaviors through a process called ritualization -thermoregulation– when overheated, heat directed to bare skin on head (comb and throat thingy) -many birds have evolved patches of bare skin for thermoregulation effects -skin gets pink and red because of blood underneath -animals get info about the state of the other individual based on redness of the skinn -this is now part of the signaling system -skin pigmented red -now a sign of arousal – sexual arousal or anger, etc |
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Evolution of Signals: Ritualization in blue footed boobies
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Courtship ritual of sky pointing
-position, biomechanically, is a flight mechanism - an intention movement for flight -when held, and exaggerated, becomes part of courtship signal |
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selection for honeybee dances
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Some stingless bees buzz when returning with food
Other species of stingless bees produce scent trails, then buzz on arrival Still other produce pulses of sound that convey distance: longer the pulse, father the food. Then the scout performs a short zigzag flight outside of the hive that is aimed towards the food source. REVIEW IN NOTES |
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APE/PARROT LANGUAGE
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LOOK OVER IN NOTES (LECTURE 16-17)
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parthogenic life cycle: rotifers
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During summer, female produces diploid egg > grows into female that produced diploid egg > continues
Mixis signal – occurs at end of summer -triggers meiosis -female begins producing haploid eggs instead of diploid eggs -develops into haploid male without fertilization -Another female on later schedule – produces her haploid eggs > now there are sperm present > eggs fertilized to produce diploid zygote, which goes dormant for the winter -when spring comes, the diploid zygote will hatch into the 2n female When environment is stable and predictable, it makes sense to produce copies of yourself When environment becomes unstable, variety/range of genotypes is more useful |
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Why have two sexes?
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Start with isogametic – one sex
-to improve competitive edge – may go to making more gametes than everybody else -to make more, you have to make them smaller (SPERM) OR -put more resources into each gamete -offspring will be physically larger/more competitive -results in fewer gametes that are larger (EGGS) Cost of making eggs mobile is large because of size, making sperm mobile has less of a cost 2 sources have different evolutionary forces working on them |
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sexual dimorphism
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clear differences in evolutions of males and females of the same species
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sexual dimorphism in elephant seals
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-being selected for a bigger size
-reason – competition among males is incredibly fierce, winner gets access to ALL females on one beach |
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sexual dimorphism in green iguanas
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want to be large in order to be competitive, but not TOO big, because if they are too big they will die in an El Nino year
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frequent arousal in male Norway Rats
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Female doesn’t want to mate a lot of times, male does – little benefit
-males more sesceptible to frequent rearousal |
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choosiness in male Mormon crickets
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-Males very choosy because mating is very expensive
-Each male produces a spermatophore – a package of sperm that can be up to one third of the male’s body weight -makes it more likely he will fertilize ALL of the females eggs -casing of spermatophore is protein rich, give female energy to make more eggs -take a long time to produce a new spermatophore – may only mate just once in a season/lifetime -will pick larger females – means they’re probably healthier, have more eggs |
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choosy males and competitive females in seahorse species
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Once female’s eggs are fertilized, she lays them in a pouch in the male body
-Male pouch is very complicated, similar to a uterus -Male seahorses essentially pregnant -Although females invest a lot in eggs, males invest a lot of energy and time in nourishing the eggs – out of the reproductive pool -Females can lay new batch of eggs quicker than male can produce sperm, so there can be much female competition for access to males, and males are choosy – tend to mate with larger females Sex role reversal |
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Mate Competion via dominance: Stumptail Macaque
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Many driving forces of selection:
-competition by dominance (fighting) – selection for bigger and stronger -selection for traits to circumvent dominance – in social species w/ dominance hierarchies Alpha male gets to mate with females, tried to prevent others from mating -alpha male hogged the vast majority of copulation -means the dominant male spend a lot of time guarding females from other males – may be why they are only dominant for 2-3 years |
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mate competition via dominance: Baboon
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Baboons
-heirarchy -dominant male However, when observed: -alpha male didn’t get huge benefit in mating with females -female baboons have estrus cycle, only fertile at certain point at each month -in baboons, female is fertile when their genitalia swells and turns pink -alpha male doesn’t interfere with copulation unless female is in estrus -males and females still copulate for other reasons, alpha male only hogs the females in estrus |
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alternate strategies to dominance: alliances in baboons
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-form between a male and a female
-anthropomorphic – assuming animals act for the same reasons as humans – shouldn’t be counted on! -allows mating without alpha male -female often has offspring from previous year, male will provide defense -they will share food, etc Alliances can also form among young males (subordinates) -hang out together, form (long-term) friendships -if one is trying to mate with female and alpha male sees them, other “friends” will hold alpha male off long enough for their “friend” and his female to get away |
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outwitting dominance: male iguanas
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Large males dislodge smaller ones before they can ejaculate;
Really small males ejaculate internally (penis is internal until actually copulating) and so transfer the ‘old’ sperm quickly |
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alternates to dominance: female mimicry in bluegill fish
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-Males make nest in gravel at bottom of lake bed
-good place to deposit eggs -guards this territory to keep other males away -the bigger the male, the bigger/better the nest location is likely to be’ Female mimicry In this picture: male, female, very young male that looks like a female -come into the male territories acting like a female, want to hang around in the territory long enough for a real female to show up -as soon as female lays eggs, male mimic spawns his sperm too -some eggs get fertilized by each -even though young male couldn’t have territory, he gained some fitness |
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alternates to dominance: satellite behavior in natterjack toads
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-males gather in one place trying to call for females
-little guys act as satellites to older males -as females come in, some will bump into the little guys, if big croaking male is busy copulating, the female will mate with the little frogs -thought they can’t compete in a croaking contest, they find a way to mate MARINE IGUANAS -Large sized males are dominant -If a female is copulating with a middle sized male, a large male will come over and try to knock smaller male off -if the smaller iguanas are aware of the presence of larger males, they will ejaculate into their own cloaca to be able to mate very quickly with female -Therefore, they will have passed more sperm if they get knocked off |
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alternates to dominance - conditional strategy in scorpionfly
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-Large males guard a dead cricket to attract female
-Medium size males produce spit bubble, drop it on leaf, females will come drink from it advantage – don’t have to go find an insect, no searching involved -Small males go not produce any kind of nuptial gift, they force copulation – female flying along and is dive bombed EXPERIMENT -set up terrarium -10 females -2 large males -4 medium males -2 small males -2 dead crickets -2 large males claimed crickets, 4 medium produced their spit bubbles, 2 smaller tried to force copulation -large males got 6 copulations each, medium got 2 each, small got 1 each -large males removed, dead crickets taken over by two largest remaining crickets -2 medium left kept producing spit bubbles, 2 small ones adopted unguarded spit bubbles because there was no one to keep them away anymore -proves that all these strategies are conditional, can change based on circumstances |
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alternates to dominance - Mixed ESS in side blotched lizards
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Orange throated males – generally largest - maintain large territories
can support up to five females Blue throated males – medium sized - also territorial, maintain small territories can support only one female Yellow throated – smallest - use “sneaker” strategy Scientist found If population was mostly orange throated and blue throated males were introduced, they generally were not very successful If you introduced yellow throated males into the same population, they were much more successful, more yellow throated babies started to show up What was going on? O males spending time/energy guarding his females, yellow “sneakers” could easily find and court females *ORANGE VULNERABLE TO YELLOW BUT NOT BLUE* In mostly blue population, yellow has very little success Blue lizards always attending their female, not vulnerable to yellow In mostly yellow population, introduce orange and they would not be very successful Introduce blue, they begin to have success because they can guarantee themselves reproductive success Circle (Orange>blue>yellow>orange…) rock paper scissors! |
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Alternative strategies to dominance in marine isopod, Paracerceis sculpta
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Marine Isopods
-lives in a marine sponge -as water flows through, brings in organic material, waste water flushed out the top -isopod grabs whatever organic material is can -3 kinds of males: alpha males – dominant, will kick other males out of sponge bete male – female mimics, comes into sponge acting like a female gamma males – “sneaker” strategy, very tiny, creep into sponge and hang out there waiting for chance to mate -evolutionary stable strategy -under some circumstances, it’s better to be one or the other alpha – best when there is one alpha, one beta, and one female (alpha is always around the female) beta – best when there is one alpha, one beta, and many females (alpha can’t guard all the females at the same time, spends a lot of energy guarding the sponge) gamma - other |
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Mate guarding in clown shrimp
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Mate guarding – idea that a male finds a female, stand by her until she is ready to mate
Happens in species where female is not always receptive Clown Shrimp – pre-copulating mate guarding -female has hard shell, not receptive to mating -can only mate right after she molts, when shell is soft -males look around for females on anemone, when they find on, guard it until she molts |
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Mate guarding in Atelopus toad
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Atelopus – females spawn right after the monsoon rains have begun
-temporary ponds – ephemeral ponds – -males start searching right before rains are supposed to start -when they find a female, they latch onto her back and ride around until the rains start -keeps other males, makes sure male is there immediately when female is ready to spawn (guarantees him a mate although it is costly – he cannot forage for food, for example) |
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sperm competition in Damselfly
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Spermoatheca – storage unit along reproductive tract that eggs pass through
-competitive males try to get rid of sperm that is already stored -penis has barbs that physically pulls other sperm out -once he has cleared out the spermatheca, he releases his own Post-copulation mate guarding – males will stay by these females to make sure other males don’t come along and do the same thing |
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Sperm competition in Dunnock
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If a male thinks the female has already mated, he pecks the chloaca
Irritates it enough that leftover sperm will be removed Females cooperate – find it beneficial to mate with a lot of males especially in case when dominant male comes along after copulation with a subordinate male |
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Copulatory Plugs in Heliconius erato
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Tries to plug up female’s opening to prevent other males from mating with her
Smells bad, other males will avoid the female generally |
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Copulatory plugs in guinea pig
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Males can completely block the vaginal opening of the female to prevent other males from mating
Physical block |
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Copulatory Plugs in orb-weaver spider
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Male inserts pedipalps into female’s genital openings. The pedipalps inflate and transfer sperm. Male then dies with pedipalps in place. Female cannot mate again.
-female can mate again after she molts, the body of the mate is ejected and she lays eggs |
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Post-copulatory mate guarding in African Elephant: managing cost
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-staying with infertile female for long periods of time – too much cost
Better off finding new one |
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Post-copulatory mate guarding in Seychelles warbler: cost-benefit analysis
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-only show post copulatory mate guarding until female is fertile
-EPC – extra pair copulations – when intruding male actually tries to mate with female on the territory -after female is fertile, no point in intrusions, mating attempts If male things eggs are already laid, he makes little or no attempt to guard females form other mates Male adjusts his efforts based on other risks |
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Post-copulatory mate guarding: Belding’s vs. Idaho Ground Squirrel
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-closely related species of squirrels but evolved very different patterns
Belding’s – colonial, many females living together females use the sperm of the first male that they mate with Idaho – solitary – spread out, separate feeding territories uses sperm of last male that they mate with If you’re solitary, it’s hard to find a fertile female once you mate, should you stay with her or go off looking for other females? If she is using last sperm and females are so spread out, beneficial to stay with female (Idaho) Belding’s - staying does not affect which sperm will be used, and other females are nearby so it is in no way beneficial |
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Sexual interference - newts
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Spermatophore transfer interference – male and female almost to point where sperm transfer takes place, intruding male waits til last moment and slips in between – catches the other male’s spermatophore and inserts his own
Amplexux (when male is mounted) interference – when intruding males does not have spermatophore, watches copulating couple, throws of copulating male and courtship is stopped (have to go back to beginning) makes it take forever, makes it more likely that the rival male will be able to come up with a spermatophore Pseudo female behavior – usually in situations where two males bump into each other and there is not female around If one males begins courtship, other male adopts female posture, prompting courtship to continue The pseudo female allows rival male to expend spermatophore uselessly Then when a female shows up, the pseudo female is ready to mate and the rival is not |
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Infanticide: langur
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Competition with other males who are no longer in power
If new males come into power, they start to kill off preexisting young – to get female to be fertile again and to take competitive male offspring out of the gene pool |
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Theories of infanticide in langur populations
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“Social Pathology Hypothesis” – a maladaptive effect of over-crowding
“Quicker Reproduction Hypthesis” Darwinian natural selection – males are trying to get females ready to mate with them “Population Regulation Hypothesis” Males are benefiting the troop by getting rid of too many babies – Group selection Group Selection issues: If male arose that sacrificed himself to rid band of excess infants, then his alleles get passed on because band survives better. BUT suppose other males in group don’t take risks. Their alleles would get passed on even more and the alleles for sacrifice would decrease in population Predictions for Quicker Reproduction Hypothesis: Males should never kill own offspring Females should resume sexual cycling Females should mate with infanticidal males |
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Lions and infanticide
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Males hunt infants under 9 mos old
Lionesses resume sexual cycling after losing infant Lionesses mate with infanticidal male If male didn’t kill infant, lioness probably would not start cycling during time male controls pride |
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Nuptial Gifts: Hilara sartor
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-gift is empty: what is the purpose?
-while female busies herself with the gift, male take opportunity to mate with her |
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Nuptial gifts: Katydid with spermatophore
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-spermatophore is part of the nuptial gift (casing provides nutrients) – will choose bigger spermatophore
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Nuptial Gifts: Sagebrush cricket
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Hind wings – fleshy lobes that are eaten by the female during courtship
prolongs the copulation, ensures more sperm is transferred |
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Nuptial gifts: Black widows and REdback spiders
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Female typically eats the male during copulation – prolongs copulation
sacrifice life to fertilize significant number of eggs |
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Territory Quality: Wrasse
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Territory – will provide food, shelter, resources
Wrasse – males make territories that attract females, territory based on location for nest quality dominant Wrasse get deeper territories, attract best females attract based on quality of territory |
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Territory quality: Parus major or Great Tit
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Many birds will choose males based on whether territory can yield enough food to feed offspring
In England, average offspring in different territories: -pine forest – 7 offspring at 7 g each -oak forest – 8 offspring at 8 g each |
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Territory quality: pronghorn antelope
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Female wander around looking for males, pick male to join up based on quality of his territory
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Sperm quality: Drosophila
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Give females a choice between older male and a virgin male, she picks the virgin
-likely reflects quantity and quality of sperm |
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Potential as a parent: Red-winged blackbird/ GOOD GENES HYPOTHESIS
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-critical in species where the female requires help or would benefit from male help in raising young
MATERIAL benefits: -blackbird with big red shoulder patch -females tend to choose males with bigger shoulder patches -shoulder patch correlates with male tendency to defend nests -birds are colonial – small territories – shoulder pads second priority after territory size -females also seem to look at courtship intensity/attentiveness -correlates with feeding of the offspring -makes female more likely to survive breeding season, have reserves for the winter, and survive to next season -in general: males with fancy plumage are healthier -benefit simply of having good genes Good Genes Hypothesis – if females choose males on basis of traits that reflect genetic quality, their offspring will have genetic quality to the females own genes will be carried on more effectively to the next generation |
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Good Genes: Satin Bowerbird
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-build structures on forest floor called a bower
then decorates it -females check for nice, strong, and well decorated bowers before deciding with whom to mate -NO material benefit, doesn’t use it as a nest, she leaves after copulation and gets no parental help -uses bower as some kind of gauge -males birds go for colorful, have decoration fights with other males -turns out the more dominant males are the ones who can hog the best decorations -female sees best decorations = more dominant male -kind of sexual selection - females use certain traits to judge quality |
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Good Genes/Leking - Peacock
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Though tail is way too long, sometimes a burden – gets female attention
-leking – males all in one spot displaying to females, showing off tails, doing courtship dance -females choose males based on size/density of their tails # of eye spots -males that are very popular will mate multiple times, unpopular male may not mate at all -study in closed off park with identified/observed peacocks – showed that within the group, some males got multiple mates every time they displayed while others didn’t get any -scientists captured males with more lush tails and clipped some eye spots off out of tail -when released back into wild, those who had eyespots reduced were then less popular Is this good genes or material benefit? -peacock males provide no parental care, no territorial advantage -must be good genes -on average, males with more lush tails are stronger, healthier One year, foxes go into park -peacocks that got caught by foxes were the ones with the smaller tails -peacocks with bigger tails more successful in getting away from the foxes Limit on sexual selection: -selection for males with bigger tails eventually caused big tails |
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Good Genes/Healthy Mates: Barn Swallow/ Hamilton-Zuk Parasite Resistance Hypothesis
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Hamilton-Zuk Parasite Resistance Hypothesis
-idea that plumage might reflect ability of birds to resist parasites (bird lice, bird mites – ecoparasites) -if females choose males with nice plumage, they will get parasite resistant males In Barn Swallow – longer tails reflect preventive ability? Could this be the case? Parasites relevant? - Barn swallows DO have ectoparasites that cause health problems (low weight in fledglings) Must be genetic – variability in resistance and it must be heritable to some extent ( (cross fostering experiment – took offspring from fathers with high parasites and put them in nests with low parasites, offspring from parasite resistant father put on nest with parasite vulnerability – offspring showed traits dependent on biological origin, not environmental situation) 3) Parasite load must correlate with tail length – observational study confirmed ( correlation found, experiment done -treated males with high parasite load with medicine that reduced parasite load, new feathers grew in longer) |
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Superb Bird of Paradise
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Mating ritual – male make electric blue wing display
Catches attention of the female -tries to impress her |
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Pre-Existing Sensory Bias: random, novel stimulus
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Idea that males try to get female attention by displaying some novel/mutant trait
Brain of the female wired to pick male based on such feature? Experiment: glued swordtail onto male platyfish Females choose males with sword tail even though their species doesn’t have sword tails Brain wired to be interested in sword tail Chart shows sword tails basically branched off from the platyfish Shows preference likely evolved before the actual swordfish |
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Pre-existing sensory bias - auklets
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Took least auklets (bird usually with no crest) and glued type of crest on their heads
Put birds out in auklet colony Females display to males in colony, females also choosy – choose on basis of crest even though their species doesn’t have a crest Choose larger crest over smaller crest, smaller crest over none at all Breast crest and control didn’t elicit very many sexual displays If birds liked novelty alone, they would probably be just as interested in the breast crest Suggests something in female that prefers crest on head (things going up seem to be more appealing) |
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Pre-existing sensory bias - guppies
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Preexisting biases may have evolved for totally different purposes
Guppies – females prefer males with more orange on their bodies Preexisting bias seems to have to do with feeding – flower with orange spots that guppies feed on Attraction to orange spots is beneficial Male with orange spot exploiting this interest |
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Runaway sexual selection?
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Suppose females evolve preference for a trait because it is a useful measure of male quality (like a pref for long tails)
Now suppose a male arises with a gene for long tails that is UNRELATED TO QUALITY. He could be totally pitiful but put all energy into a long tail. Females with genetic pref for long tails would be stuck: they’d be totally won over by the genetically long-tailed male Result: now have sexual selection for a long-tailed gene that exists unrelated to quality Only selected against by natural selection. Will be lost from population only when natural selection outweighs sexual selection – if, for example, the trait is so bad the males don’t survive long enough to mate Result: Sexual Selection runs away with the male trait Even though the trait might be detrimental it will be selected for – because a male w/o the trait, say a short-tailed male, won’t be selected by females so would be an evolutionary dead end. |
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Result of sexual selection - Irish elk
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-amount of energy put into growing these antler could be very costly
-couldn’t survive lower amounts of food during mini Ice Age -all male fossils found in peak bogs of Ireland – could have wandered out and gotten stuck |
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other results of sexual selection
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-Sometimes female suffer from certain male traits
-female fitness declines > those that survive are less interested in the trait > interest for trait decreases > male attractiveness declines > trait gets more dramatic to elicit a response |
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Drosophila: female resistance to negative consequences of mate choice
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LOOK UP IN BOOK
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monogamy
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1 female, 1 male
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polygyny
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1 male, many females
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polyandry
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1 female, many males
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promiscuity
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may males, many females
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monogamy: Atelopus frogs
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-male mounts the female until the rain comes
-guarantees ONE mate -although male doesn't get to mate with many females, he does guarantee the one, where as he could get none if he did not guard her |
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mate assistance monogamy: silver backed jackals
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Silver backed jackals
Whelp young in underground Hard for males to provide food for all – because of this they tend to only have one mate ASSISTANCE IS REQUIRED – if they abandoned the female, the puppies WILL die and the male’s fitness would be zero |
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mate assistance monogamy: hornbills
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-Female goes into hole and lays eggs, male brings back grass mud etc to seal off the hole (keeps predator out)
-Therefore female is unable to look for food while incubating the eggs and raising the young -Male outside goes to find food and bring it back to the nest -Male probably unable to maintain other “family” because energy is spent feeding the first; females generally do not accept a male who already has a mate |
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female enforcement monogamy: burying beetles
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Males would be polygamous if females will let them
Burying beetle – males make mounds of dirt and manure, attract females -females arrive, mate, deposit their eggs, then push the male down off the mound so he cannot release any more pheremones |
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female enforcement: great tit
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Two kinds of nesting sites:
-deciduous oak forest – most popular, higher fitness (more food), higher quality males – avg 8 offspring 8g -coniferous pine forest – less popular, lower quality males – avg 7 offspring, 7g Cost of being polygamous – loss of male help EXPERIMENT Allowed pairs to form territories and mate in an oak forest After eggs were laid, male was removed Female raising young in oak forest without help – she raises six offspring, and they are very small (6g) enforced monogomous |
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Polygyny Threshold Model: Red-winged Blackbird
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In some species, females choose polygyny
In many bird species females can choose to be second of third mate, or can choose monogamy Polygyny Threshold Model – Female should choose polygyny only if her fitness is at least equal to the fitness of monogamy Territory quality should matter - high quality territories should fill up first Early arriving females should get best territories Monogomous territories should be the lower quality territories Red winged blackbird – live in clusters in marshes Best territories – ones overhanging water, then central, then ones near dry land territories provide shelter, if you are overhanging water you are better protected EXPERIMENT Manipulated nesting habitat and compared territories These females almost always choose monogamy However, if given the choice of a good territory of a bad territory, they will choose territory over monogamy male help has less of an effect on fitness than does the protection from predators Female rwb almost always choose monogamy (unpaired male on his territory) Researchers identified pairs of similar nesting territories and manipulated amount of nesting habitat (increased it on one of the pair) If given choice between a mated male whose territory has good nesting habitat (cattails over water) and an unmated male whose territory lacked good habitat, female now chose mated male (POLYGYNY) Females that made this choice had about twice as many offspring as latecomers that had nest on land in monogamous males territory |
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resource defense polygyny: cichlids
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Get snail shells, female deposits eggs in snail shells
Males will gather as many snail shells as they can, attract more females Resource – defense polygyny Male traits not as important to the female in this case |
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Female Defense Polygyny: Lions
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-females cluster for hunting and defense
Cooperative hunting, cooperative defense |
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Female Defense Polygyny: Elephant Seals
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– females cluster on rare breeding beaches
Females have to give birth on land – only certain stretched of beach are acceptable to give birth on Creates clusters of females, allow males to get access to certain group of females |
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Female Defense Polygyny: Oropendola
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– females are colonial for defense
Females live in colony because male defends them |
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Polygyny: Yellow Bellied Marmots
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Benefits of polygyny for females is presumably a high-quality male who competes well. Assumption is that such females will have higher fitness. But…Yellow-bellied marmots
General advantages to females include protection and healthier, more competitive males Breeding was puzzling for a long time: -male territories are mixed – some monogamous and some polygamous (contained 1-5 females) -scientists looked at number of females vs. number of offspring in one year, got negative correlation (in other words, the more females there were on the territory, the worse of they were – opposite result of red winged blackbird) -looked at lifetime fitness – got same result Looked deeper into situation -found females were living either by themselves or in clusters and males competed among themselves for access to the groups -dominant males tended to get larger groups -benefit to females : larger males? Turns out, clusters are matrilineal groupings (aka daughters stay with their mothers) end up with several females living in same territory (related ones) sometimes females leave and form their own monogamous territory, sometimes they don’t Looked at dispersal if territory was filled up, all daughters would leave if they weren’t filled, results were mixed Found that dispersal is very high risk – lost of costs (increased risk of predation, risk of not finding another good territory) MIXED ESS? -some individuals likely to be risk takers while others aren’t -female clusters could be due to reduced risk |
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Scramble Defense Polygyny: fireflies
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-females do not cluster
-Females scattered randomly Males fly around looking for females, copulates, then keeps flying around – extent of interaction |
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Lek Polygyny: Hotspots & Peacocks
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Why would males form leks? (be close together)
Hot spots – males all go to hot spot because they can find a lot of females there Hot spots often in places where there is a lot of food |
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Lek Polygyny: Spruce grouse & hotspots
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-males form in one place and stomp around
-females mate with the one or two most dominant males -hotspots don't have to do with geographic location, just with number of females |
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Lek Polygyny: Hotspots and Hammerhead Bats
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-males display along riverbanks which females use as flyways
Males hang upsside down from trees and make clanking noises – loudness and deepness reflect male size Along river where females are (lots of insects) Females patrol and check out the males |
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Lek Polygyny: Little bustards & hotshots
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Hot shots – the presence of an attractive male lures in females, the presence of many females brings in more males
Little bustard – females would come investigate male decoys, then males would follow (many females per male) QUALITY of the decoy mattered! Dull decoys attracted fewer birds Leks start to fall apart once they get too large, only dominant males can maintain leks |
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Lek Polygyny: Great Snipe Hotshots
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Males have small display territories next to each other
If remove one subordinate male, it is quickly replaced by another subordinate male If remove central dominant males, the subordinates just leave and the lek falls apart |
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Lek Polygyny: More Hotshots – Black Grouse
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Geographic location important in this case
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Lek Polygyny: More Hotshots – Marine Iguanas
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Location of a particular male matters in this case, not geographical location
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But why form leks at all? Male point-of-view
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Opportunity for young males to benefit via satellite behavior
Social defenses Signal amplification brings in more females for less effort than, say, scramble defense polygyny Got to go where females are (i.e., frogs at pond, horseshoe crabs on beach, hammerhead bats) |
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But why form leks at all? Female point-of-view
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Requirement for particular habitat for breeding (i.e., frogs at pond, horseshoe crabs on beach, hammerhead bats)
Social defenses Opportunity for comparison shopping |
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Why are females willing to mate with more than one male?
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Fertility insurance
Good Genes Genetic Compatibility Types of mating with multiple males: Extra pair copulation (socially monogomous) Promiscuity – sequential mating Polyandry |
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Bluethroats & Social Monogamy
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Extra pair copulation
Mating system looks monogomous, paternity however is not monogomous some eggs fathered by social mate, some fathered by other males from different territories Generally with equally or less dominant males Observation – notice that the offspring from the EPCs had better immune responses than the offspring from the social mate How does the female now that she is genetically more compatible? |
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extra pair copulation
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Mating system looks monogomous, paternity however is not monogomous
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Superb Starling – Social Monogamy
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A female whose social mate was less heterozygous than she was more likely to mate outside the bond
Offspring from the EPC were more heterozygous (more genetic variety) GENETIC COMPATIBILITY |
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Dunnocks & Promiscuity
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-Mating system depends on food density. Food density determines whether feeding areas overlap or not so determines how many males the female regularly encounters
-Both males and females set up their own feeding territories -breeding depends on territory overlap -will mate with all males that overlap, get’s child raising help from all of them |
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Polyandry: Spotted Sandpipers
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Females arrive on breeding grounds first, set up territories, and fight each other for prime territories. Males pick territories and mate with resident female. If second male arrives, female also mates with him. If a third arrives, she’ll mate with him. Males rear clutches without female help (usually).
How did this evolve? Stage set: Female sandpipers can only lay 4 eggs at a times. To take advantage of abundance must lay another whole clutch. Sandpipers as a group are ground nesters with heavy predation pressure, spotted sandpipers have evolved to nest on small islands which reduces predation pressure, so just one parent needed to raise offspring Most sandpiper species are monogamous – to deal with predation pressure Offspring are precocial Spotted sandpiper – like islands (island nesters) to avoid predation -now this means monogamy isn’t required to prevent predation -females mutated in this direction first (behavior to leave nest and go lay another clutch with another male) -If male mutated as well, nobody would raise the offspring and fitness would be 0 – so basically, females evolved first so they win |
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reciprocal altruism: vampire bats
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ALTRUISM - speculation
-Group selection – doesn’t make sense since one unit of inheritance is what evolution is based on very vulnerable to mutation for selfish behavior – mutant would benefit from everyone else’s selflessness and pays no cost selfish mutant fitness would increase, selfless behavior would decrease, altruism would be lost -Kin selection – fitness through relatives could justify self-sacrifice |
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altruism: Alarm Calling in Belding’s Ground Squirrel
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Two alarm calls: one for hawks and one for terrestrial predators like coyotes and weasels.
Both males & females warn for hawks. Only females warn for terrestrial predators When hear alarm call for hawks the colonial squirrels dash quickly for burrows. Caller is protected by confusion effect. When hear alarm call for terrestrial predator, squirrels look to see where predator is and retreat carefully. Caller is targeted by predator. Colonial species Males disperse away from colonies while females stay – colonies mostly females 1 call is not altruistic – the caller benefits from the confusion effect 2 is altruistic So, only females being altruistic. Why? Possibly because of 1) parental care of own young or 2) indirect benefits via nieces & nephews, etc. Evidence favors indirect because when males have fathered offspring, they still don’t call. And females that have yet to produce offspring always call. So parental not supported. Colonial & females related to most squirrels. Males have come from other colonies. So females should and do call, and males shouldn’t and don’t. Kin selection – would explain why females call and males don’t Females are related to many in the colony, males are not Direct fitness – goes through offspring Indirect fitness – goes through relatives Inclusive fitness – direct + indirect When a squirrel makes terrestrial call, they are risking direct fitness but increasing indirect fitness, so if they are overall increasing their inclusive fitness, this makes sense! |
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direct fitness
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through offspring
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indirect fitness
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through relatives
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inclusive fitness
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total of fitness through both offspring and relatives
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Cooperative Breeding: Pied Kingfisher
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Sex ratio is male-biased so often young males cannot compete for mates . In their first year of breeding, unmated males take one of three options: Primary helper (help parents), secondary helper (help unrelated pair), or delayer (no help, just delays)
These bird who do not have own offspring will help others breed Cohort of unmated males – choose between 3 options: -primary helpers – help their parents raise their siblings -seconday – help an unrelated couple raise offspring -delayers – don’t help anyone Why are there these three types? Seems as though only primary helpers get indirect fitness Graph – primary helpers work much more than secondary – pay a much higher cost o – number of offspring r – relatedness of those offspring s – survival to second year m – mating success Primary helpers – total .99 fitness, although there is a cost it is offset by increased fitness For secondary helper, mating success greatly increased because they were able to mate with the females they had helped the previous yesr had demonstrated health and reliability, good pick for female Why not be a primary helper? Secondary helpers actually can not locate their own parents, or have been pushed away by father (too many males already) Delayers – very low success – probably just substandard individuals, not as healthy, no popular some just may be unlucky and could not find someone to help |
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Cooperative Breeding Acorn woodpecker: Effects of Habitat Saturation
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Collect acorns in fall, drill holes into oak trees, store acorns in dead wood in trees
Eat these acorns all winter long Acorn storage tree is essential, number of trees appropriate to store acorns are limited especially in urban areas Habitat saturation – all available trees are being used and the young have no place to go to establish own trees instead stick around and help raise their siblings – increase indirect fitness Graph – high saturation means high percentage of helping, same with medium and low |
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Cooperative Breeding White-fronted bee-eater: low food availability
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Food availability predicts whether the young will establish own nests or stay and help parents raise offspring
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Cooperative Breeding: Seychelles warbler
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Dispersing percentages – if they can find their parents they are less likely to disperse, more likely to stick around and help
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Cooperation in Acquiring a Mate: wild turkeys
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Leking species
Within lek there are subgroups, competing for females females select subgroups based on the complexity of a synchronized display Turns out the subgroups are comprised of brothers, all helping one brother dominant brother is the only one who gets to mate dominant male gets direct fitness, all the rest get indirect fitness |
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Cooperation in Acquiring a Mate: long-tailed manakins
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Not always indirect fitness!
Two males – one jumps up and then the other jumps up, make pinging sound Females check out this display – attracted to more complex displays Display becomes more complex – take a lot of coordination Only one of these males gets to breed (only the dominant) Why does the subordinate male help? He is not related! Subordinate males accept this position because in the end it is the only way to get fitness after years of being “apprentice” |
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eusociality
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Eu – true
Extreme social behavior |
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Eusociality: honey bees
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Eu – true
Extreme social behavior Bee heirarchy: queen (produces all the eggs) female workers (never breed) male drones (do no work) How did this evolve? Worker bees make sacrifice, never directly benefit Haplodiploidy – genetic system in which males are haploid and females are diploid – if egg gets fertilized, it hatches a female, if it does not it hatches into a male Because male is haploid, only has one type of chromosomes to offer so daughters are always AT LEAST .5 related (.75 average) sisters very highly related!!! Because of haplodoploidy system raising a sister more productive then raising a daughter |
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eusocialty in naked mole rats
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Dominant female breeds, dominant male breeds
Other members of colony do not breed – they raise young and forage for food Termites show eusocial behavior as well – king and queen breed while others are helpers These colonies highly inbred, helping everyone else doesn’t hurt |
